Work loading, unloading, and positioning means for handling sheet material in power presses and the like

ABSTRACT

Work loading, unloading, and positioning means for handling sheet material for power presses and the like is provided with reversible power driven rollers for both loading and unloading of sheets. In the case of sheets constructed of ferromagnetic material, magnetized drive rollers are used to move the sheets against forward positioning or locating stops that extend above and below the pass line to arrest movement of the sheets. In one embodiment of this invention, each sheet is moved against a positioning or locating side stop extending upward from the press bed, by power means that bodily moves the drive rollers sideways. In other embodiments of this invention, a sideways pusher, in the form of a spring or a power operated device, moves the sheet sideways against the side stop. To improve side pusher operation, the magnetic field of the drive rollers is pulsed, and in the case of the power operated side pusher, energization thereof is alternated with energization of the drive roll magnetic system. In still another embodiment of this invention, two sets of axially aligned drive rollers have their magnetic fields alternately energized to prevent the sheets from coming to rest in a skewed position. After the press is operated, rotation of the drive rolls is reversed to retrieve the sheet and deliver it to a stacking means.

Elnited States Patent Fowler [451 Sept. 30, 1975 Alexander Fowler, 334 Westover Rd., Stamford, Conn. 06902 22 Filed: Aug. 2, 1973 211 App]. No.2 384,888

[76] lnventor:

[52] U.S. Cl. 271/3; 83/157 X; 83/419 X;

271/236; 271/241; 271/250;271/D1G. 3 [51] Int. Cl. B6511 5/06; B65H 9/10 [58] Field of Search 27l/5860,

271/52, DIG. 9, 3, 53, 48, 236, 237, 238, 241, 250, DIG. 3; 83/436, 422, 419, 420, 157, 253; 198/41 Primary Examiner-Evon C. Blunk Assistant Examiner-Bruce H. Stoner, Jr.

Attorney, Agent, or Firm-Ostrolenk, Faber, Gerb &

Soffen [5 7 ABSTRACT Work loading, unloading, and positioning means for handling sheet material for power presses and the like is provided with reversible power driven rollers for both loading and unloading of sheets. In the case of sheets constructed of ferromagnetic material, magnetized drive rollers are used to move the sheets against forward positioning or locating stops that extend above and below the pass line to arrest movement of the Sheets.

In one embodiment of this invention, each sheet is moved against a positioning or locating side stop extending upward from the press bed, by power means that bodily moves the drive rollers sideways. In other embodiments of this invention, a sideways pusher, in the form of a spring or a power operated device, moves the sheet sideways against the side stop. To improve side pusher operation, the magnetic field of the drive rollers is pulsed, and in the case of the power operated side pusher, energization thereof is alternated with energization of the drive roll magnetic system. In still another embodiment of this invention, two sets of axially aligned drive rollers have their magnetic fields alternately energized to prevent the sheets from coming to rest in a skewed position.

After the press is operated, rotation of the drive rolls is reversed to retrieve the sheet and deliver it to a stacking means.

7 Claims, 8 Drawing Figures US. Patent Sept. 30,1975 Sheet 1 1 1 3 9%,980

US. Patent Sept. 30,1975 Sheet20f4 3,908,980

US. Patent 'se r. 30,1975 Sheet4 0f4 3,908,980

WORK LOADING, UNLOADING, AND POSITIONING MEANS FOR I-IANDLING SI-IEET MATERIAL IN POWER PRESSES AND THE LIKE This invention relates to loading and unloading apparatus in general and more particularly relates to apparatus of this type for accurately locating ferromagnetic blanks in power operated machines.

In these days, when there is an emphasis on safety in connection with the operation of power presses and other power operated machines for working sheet material, it is very desirable and sometimes mandatory that the operator not be required to have access to the work station of the press where the press ram drives the die elements into engagement with the blank sheets. Because of the foregoing, it is often desirable to provide power operated loading and unloading means for the sheets. An example of this type of unloading apparatus is disclosed in U.S. Pat. No. 2,976,753 issued Mar. 28, I96], to A. Fowler et al. for a Press Unloader Including Magnetic Lift Means and Magnetic Delivery Rollers.

In accordance with the instant invention, electromagnetic feed rolls of the type described in U.S. Pat. No. 3,228,680, issued .Ian. 11, 1966, to A. Fowler for a Magnetic Feed Roll System are used to both load and unload a power press. In loading the press the magnetic rolls move each sheet along a feed path from a loading station forward to a work station disposed between the ram and bed of the press. Front stops intercept movement of the sheet along the feed path, and additional means are provided to move the sheet sideways against a side stop. When the sheet is engaged with both the front and side stops, the sheet is accurately positioned to be operated upon by the press. The forces operating to deliver the sheet to its proper working position continue to act as the press ram descends.

This is in contrast to the prior art, and especially prior art manual techniques in which the operator moved the blank forward against the front stops and then sideways againsta side stop. At this point the operator was required to remove his hands, allowing a machine to perform a punching, drawing, piercing, bend, or other operation. Thus, the operator was never certain that the sheet being fabricated was in precise position at the work station. For some applications, in order to overcome improper placement of a sheet at the work station, because of operator error or vibrations of the press, the bed of the press was provided with pins or other upwardly extending elements forming a nest" that surrounded the sheet on all sides thereof. Sheets suitable for nesting must be very accurately cut, and it takes much longer for an operator to insert and remove a sheet from a work station when using a nest, as compared to indexing stops only at the front and one side of the sheet at the workstation.

After press operation is completed, rotation of the feed rolls is reversed and the sheet is withdrawn and directed to a receiving skid placed beneath a support table at the feeding station. When the feed rolls are operated in reverse. the support table is tilted so that the front end thereof is raised and the bottom of the support table intercepts the sheet being withdrawn from the work station to deflect the sheet downward toward a chute leading to the skid.

Accordingly, a primary object of the instant invention is to provide improved apparatus for loading and unloading of sheets from a power press and the like.

Another object is to provide apparatus of this type which accurately positions the sheet against indexing stops at the working area between the ram and bed of the press.

Still another object is to provide apparatus of this type in which reversible magnetic rollers are used for both loading and unloading sheets.

A further object is to provide apparatus of this type having improved conditions of safety.

A still further object is to provide apparatus of this type in which the magnetic feed rolls are energized intermittently so that side pusher means will be effective to drive the sheet sideways against the side stopper.

Yet another object is to provide apparatus of this type in which two sets of alternately energized magnetic feed rolls are utilized to prevent a sheet from being hung up out of contact with one of the positioning stops.

These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanyingdrawings in which:

FIGS. 1 and 2 are perspectives showing loading, unloading, and positioning apparatus constructed in accordance with teachings of the instant invention and operated in conjunction with a power press. In FIG. I a sheet is being fed to the work station between the ram and bed of the press, and in FIG. 2 the sheet is being withdrawn from the work station.

FIG. 3 is an electrical schematic of the apparatus of FIG. 1.

FIG. 4 is a side elevation showing a portion of the rear edge of a sheet operatively positioned at the work station. I

FIG. 5 is a plan view illustrating another embodiment of this invention and a skewing problem that may occur when feeding very thin sheets.

FIGS. 6 and 7 are views similar to FIG. 5, illustrating still another embodiment of this invention that provides a solution to the skewing problem illustrated in FIG. 5.

FIG. 8 is a plan view illustrating a further embodiment of this invention in which the magnetic feed rolls are bodily movable sideways to move the sheet against the side stop.

Now referring to the figures and more particularly to FIGS. 1-4.

Magnetic drive roller unit 10, of a type described in detail in the aforesaid U.S. Pat. No. 3,228,680, is located between a supply station indicated generally by reference numeral 11 and a work station indicated generally by reference numeral 62. Feed station 11 includes generally horizontal support table 12 pivotally mounted near its rear end on shaft 13 that extends across the upper portion of stationary frame 14. For a reason to be explained hereinafter, solenoid 15, secured to frame extension 16 and provided with plunger extension 17 secured to table 12 to the rear of pivot 13, is actuable to draw the rear end of table 12 downward, thereby raising the front end thereof. Mounted to frame 14 near the front thereof is reversible motor 18 that drives roller unit 10 through belt 19 and a suitable pulley (not shown) keyed to shaft 21 (FIG. 4) that is rotatable in bearings supported by frame 14.

When roller unit 10 is driven in a forward direction, indicated by arrow A in FIG. 4, it is effective to drive sheet 25 forward, carrying it from the upper support surface of table 12 to the upper surface 26 of die bed 27 mounted in punch press 30. Bed 27 is located below ram 28 that is mounted for downward vertical movement so that die means 29 at the lower end of ram 28 is operable to pierce selected areas of sheet 25 when the latter is in operative position at work station 12, with the forward edge 31 of sheet 25 engaged with front stops 32, 33 and side edge 35 of sheet 25 engaged with side positioning stop 34.

Front stops 32, 33 are positioned in the feed path along which sheet 25 is moved by magnetic roll unit 10, thereby arresting forward movement of sheet 25. Pusher 37, operated by energization of solenoid 38 to move from right to left with respect to FIGS. 1 and 2, engages the other side edge 39 of sheet 25 to drive side edge 35 thereof against side stop 34. As will hereinafter be explained in more detail, when solenoid 38 is energized, roller unit is not necessarily continuously energized, so that the holding force of the magnetic field of the latter will not prevent pusher 37 from driving sheet 25 against side stop 34.

After punch press 30 operates on sheet 25, ram 28 is raised, solenoid is actuated to raise the front end of table 12, and the rotation of drive motor 18 is reversed to reverse the direction of rotation for magnetic roll unit 10. It is noted that front stops 32, 33 are located so that with the front edge 31 of sheet 25 abutting stops 32, 33 a portion of sheet 25 adjacent the rear edge 41 thereof engages roll means 10 (of FIG. 4). Thus, when rotation of roll unit 10 is reversed, sheet 25 is moved to the rear toward loading station 11. However, support table 12 is now located across the feed path, so that the bottom thereof deflects sheet 25 downward to chute or ramp 42 that is positioned below table 12. Ramp 42 is secured to frame 14. and is inclined downward and rearward toward skid 43, where the finished sheets are accumulated in a topfed stack. The electrical operation of the apparatus of FIGS. 1 and 2 will now be explained, with particular reference to FIG. 3.

The closing of main switch 49 connects A.C. source 48 across lines L-l, L-2. Normally, operation of the apparatus begins when ram 28 is at the top of its stroke, so that upper limit switch 51 is closed. This energizes forward relay KF through a series circuit consisting of switch 51 and normally closed contacts KR-l of reverse relay KR. The closing of relay KF closes normally open contacts KF-l in parallel with switch 51, so that relay KF remains energized as ram 28 descends. The closing of contacts KF-l applies an AC. voltage to the input of bridge rectifier 53 through a series circuit including contacts KF-l and normally closed contacts KS-l. The DC. output of rectifier 53 is applied through series rheostat 54 to energizing coil 55 of magnetic roller unit 10. Energization of relay KF also closes contacts KF-2 and KF-3 to energize motor 18 for rotation in the forward direction. The energizing circuit for motor 18 in the forward direction is from line L-] through contacts KF-2, motor field coil 18b, contacts KS-3, motor armature 18a to line L-2.

When ferromagnetic sheet 25 is placed on support table 12 with the leading edge portion of sheet 25 resting on magnetic roller unit 10, sheet 25 is driven forward past side stop 34 until forward edge 31 of blank 25 engages front stops 32, 33. This brings about energization of relay KA from transformer 57 in that sheet 25 acts as a conductor bridging the gap between front stops 32, 33 to complete a series circuit including relay KA and normally closed contacts KR-7 across low voltage secondary winding 59 of transformer 57, whose primary winding 58 is connected directly across lines L-l, L-2. Energization of relay KA closes normally opened contacts KA-l and normally closed contacts KR-5. Energization of relay KS closes normally open contacts KS-2. opens normally closed contacts KS-l and energizes pulser device 60 through a circuit extending from line L-l through the still closed normally opened contacts KF-l and contacts KS-2 to pulser energizing terminal 63. The other pulser energizing terminal 64 is connected directly to line L-2. Pulser device 60 may be a cam-type recycling timer or an electronic unit such as a modified square wave generator.

When pulser device 60 is energized and normallly closed contacts KS-l are opened, energization of rectifier bridge 53 is now controlled by pulser device 60. That is, when pulser device normally opened contacts CS-l are closed, the input to bridge 53 will be energized, thereby energizing winding 55 of roller unit 10. When contacts CS-l are closed, normally closed pulser contacts CS-2 in series with pusher solenoid 38 are opened to deenergize the latter. Similarly, when contacts CS-2 are closed to energize pusher solenoid 38 and move pusher 37 to the left with respect to FIG. 1, contacts CS-l open and magnetic roller device winding 55 is deenergized so as not to exert a holding force that would interfere with movement of sheet 25 against positioning side stop 34.

When blank 25 finally contacts stop 34, blank 25 acts as a jumper between stops 33 and 34 to close the low voltage energizing circuit for relay KB. One end of relay coil KB is connected to one terminal of low voltage secondary winding 68 of transformer 66 whose primary winding is connected directly across lines L-l, L-2. The other end of relay winding KB is connected to stop 34 through conducting sheet 25 to stop 33, and through normally closed contacts KR-7 to the other terminal of secondary winding 68. Energization of relay KB closes normally open contacts KB-l to complete the energizing circuit for press trip relay KTP through contacts KB-l, normally closed contacts KR-S, and normally open contacts KA-l, which are closed when sheet 25 acts as a jumper between front stops 32, 33.

The energization of press trip relay KTP closes a set of contacts (not shown) in a circuit that causes press ram 28 to descend and perform a fabricating operation at bottom of its stroke, at which time lower limit switch 52 is closed to energize reverse relay KR through a circuit including lower limit switch 52 and normally closed contacts TR-l. Energization of relay KR closes normally open contacts KR-6 in parallel with lower limit switch 52, thereby maintaining deflector solenoid l5 energized despite opening of lower limit switch 52 as ram 28 rises. At the same time, contacts KR-6 maintain relay KR energized.

The energization of relay KR opens normally closed contacts KR-l in series with forward relay KF to deenergize the latter. This opens contacts KF-2 and KF-3 and simultaneously closes contacts KR-3 and KR-4 to place reverse polarity on motor field coil 18b to reverse the direction of rotation of motor 18. At the same time, magnetic roller unit 10 is energized through the energization of coil 55 in that bridge 53 is energized through contacts KS-l and KR-2. The energization of relay KR opens contacts KR-5 to deenergize relay KS. which opens contacts KS-2 and deenergizes pusher solenoid 38. Deflector relay 15 for elevating the front of table 12 is energized through a circuit including "normally open contacts KR-6. It is noted that contacts K'R-3 and KR-4 are time delayed in closing so that relay 15 tilts table 12 before motor 18 reverses and acts to cause blank 25 to be moved from left to right with respect to FIG. 1, from work station 62.

When motor 18 reverses, coil 55 of magnetic roller unit is fully energized and deflector solenoid is energized, so that the front of table 12 is raised. Magnetic roller means 10 rotating in the reverse direction moves sheet to the rear under elevated table 12, so that the trailing end of blank 25, still attracted to magnetic roller 10, trips limit switch 70 adjustably mounted to chute 42. Tripping of switch 70 closes the energizing circuit for relay TR. This opens normally closed contacts TR-1 in series with reverse relay KR, deenergizing magnetic roll energizing coil 55 in that KR-2 now opens, thereby releasing sheet 25 so that itfalls on the upper surface of chute 42 and is guided thereby to skid 43. At the same time deflector solenoid 15 is deenergized in that contact KR-6 opens, and motor 18 is deenergized by the opening of contacts KR-3 and contacts KR-4. When ram 28 reaches the top of its stroke, upper limit switch 51 is closed and the apparatus is ready to receive another sheet 25 and be operated through another cycle. The embodiment of FIG. 5 is the same as the embodiment of FIGS. 1-4 except that solenoid operated pusher 37 is replaced by spring pusher 71 secured at one end thereof to block 72 adjustably mounted on die bed 27. Pusher 71 is a curved leaf spring shaped to engage edge 39 of sheet 25 shortly after the leading portion of side edge moves forward of side stop 34. The sideward pushing action of spring pusher 71 is continuous, but the effect thereof is retarded when magnetic roller means 10 is energized. Thus, in the embodiment of FIG. 5, just as in the embodiment of FIGS. 14, the magnet coil of roller means 10 is alternately energized and deenergized under the control of a pulse generating means active when sheet 25 engages either of the front stops 32, 33. Notwithstanding the alternate energization and deenergization of the magnetic field for roller means 10, when blanks of very thin gauge ferromagnetic material are being handled, the magnetic attracting force of roller means 10 is reduced to the point where sheet 25 may become wedged or hung-up in the solid line position of FIG. 5, wherein sheet 25 is in a skewed position in firm contact with stops 33 and 34 but clear of stop 32.

In order to avoid the skewing condition illustrated in FIG. 5, the double magnetic roller means arrangement of FIGS. 6 and 7 is provided. This latter arrangement includes magnetic roller means 73 and 74, both keyed to driven shaft 75, and positioned on opposite sides of center line 76 that extends parallel to the sheet feed path and midway between front stops 32, 33. Once the forward end of side edge 35 moves forward of side stop 34 and forward edge 31 of blank 25 engages either of the front stops 32, 33, the magnetic fields of roller means 73, 74 are energized alternately. Thus, if sheet 25 initially assumes the skewed position of FIG. 6 in contact with stops 32 and 34 but clear of stop 33, each time the magnetic field of roller means 74 is energized, roller means 74 will act to pivot sheet 25 counterclockwise about side stop 34, thereby driving front edge 31 toward the other front stop 33 until sheet 25 reaches the solid line working position of FIG. 7 in engagement with all three stops 32, 33, 34.

FIG. 8 illustrates another embodiment of this invention in which the functions of the side pusher means 37 and 71 are performed by solenoid 80. Energization of solenoid moves shaft 81 axially to the left with respect to FIG. 8 and in so doing bodily moves magnetic roller units .82, 83 to the left, in that the latter are affixed to shaft 81 so as to be driven thereby and so as to be fixed in axial position thereon. When solenoid 80 is deenergized, a spring device-(not shown) drives shaft 81 to the right into engagement with stop surface 84. Shaft 81 extends through and is supported near its ends by shaft bearing units 87, 88. Pulley 91, mounted on spline section 86 of shaft 81 in a position outboard of bearing 88, is in driving engagement with shaft 81. A spider (not shown) secured to frame element 99 that supports bearings 87, 88 prevents left or right movement of pulley 91. Belt 19 provides a driving connection to pulley 91 from pulley 98 driven by reversible motor 18 (FIG. 1).

In the embodiment of FIG. 8, when sheet 25 is driven forward by roller units 82, 83,-side edges 35, 39 of sheet 25 are in the phantom positions, so that left edge 35 is considerably to the right of side stop 34. When front edge 31 of sheet 25 engages-front stops 32, 33, solenoid 80 is energized, thereby'bodily moving roller units 82, 83 to the left. Since sheet 25 is firmly held by magnetic roller units 82, 83, sheet 25 is also moved to the left to the solid line position of FIG. 8, wherein left side edge 35 is in engagement with side stop 34.

While the instant invention has been described in connection with the handling of electrically conductive sheet material that acts as ajumper to complete various circuits between stops 32, 33, and 34, it should be apparent to those skilled in the art that strategically positioned switch devices, such as microswitches or proximity devices, may be utilized, with such switch devices being actuated either directly by the sheets or by deflection or deformation of stops 32, 33, 34, or portions thereof. It is also noted that even though this invention has been described in connection with the handling of ferromagnetic sheet material, it should now be apparent to those skilled in the art that many features of this invention may be utilized with apparatus for handling non-conductive or non-magnetic material. In the latter case, pinch rolls, such as the'type illustrated in the aforesaid US. Pat. No. 3,228,680, may be provided for driving the sheets along the feed .path. Further, for some applications the sheet moving rollers may be provided with permanent magnetsjrather than electromagnets. For the permanent magnet construction, means will also be provided for pulling the sheets from the feed rollers after withdrawal of the work from the press.

Although in the foregoing preferred embodiments have been discussed, many variations and modifications will now become apparent to those skilled in the art and it is therefore understood that this invention is not limited by the disclosure but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning said stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement ofits leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means includes electromagnetic sheet holding means divided into first and second portions spaced along the rotational axis of said roller means and positioned on opposite sides of a center line for said feed path. and means for energizing each of said portions while the other is deenergized.

2. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path. power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stopmeans, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means being positioned to engage a trailing edge portion of a sheet engaged with said front stop means; and means for reversing rotation of said roll means whereby the latter retrieves the sheet from said work station; means at said feeding station defining a support for a sheet having its leading edge portion engaged by said roll means; a receiving means to the rear of said roll means opcratively positioned to receive sheets retrieved from the work station by said roll means, and means active upon reverse rotation of said roll means to direct sheets from said roll means to said receiving means; said receiving means being positioned below the support; said means active upon reverse rotation of said roll means including said support and means for tilting said support by raising its front edge above its rear edge and above said feed path.

3. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said means for moving a sheet sideways including spring means along the other side of the feed path and engageable with a side edge of a sheet at said work station urging the other side edge of said sheet against said side stop means, said roll means including pulse operated electromagnetic sheet holding means.

4. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this.

sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving'a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said means for moving a sheet sideways including a power operated pusher means along the other side of the feed path and engageable 'with a side edge of a sheet at said work station urging the other side edge of said sheet against said side stop means, said roll means including electromagnetic sheet holding means, said holding means andsaid pusher means being alternately energized.

5. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machinefrom a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear ofsaid work station positioned to engage a sheet at said supply station and upon forward rotation'of said roll means drive this sheet forward until movement thereof is arrested by engagement ofits leading edge with said front stop means, means for moving a sheet sideways to move aside edge of a sheet at said work station against said side stop means, said roll'means including magnetic sheet holding means, said roll means being positioned to engage a trailing edge portionof a sheet engaged with said front stop means; and means for reversing rotation of said roll means whereby the latter retrieves the sheet from said workstation, means at said feeding station defining a support for a sheet having its leading edge portion engaged by said roll means; a receiving means to the rear of said roll means operatively positioned to receive sheets retrieved from the work station by said roll means; and means active upon reverse rotation of said roll means to direct sheets from said roll means to said receiving means; said receiving means being positioned below the support; said means active upon reverse rotation of said roll means including said support and means for tilting said support by raising its front edge above its rear edge and above said feed path.

6. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stopmeans, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means including magnetic sheet holding means, said roll means being positioned to engage a trailing edge portion of a sheet engaged with said front stop means; and means for reversing rotation of said roll means whereby the latter retrieves the sheet from said work station; said means for moving a sheet sideways including spring means along the other side of the feed path and engageable with a side edge of a sheet at said work station urging the other side edge of said sheet against said side stop means; said sheet holding means being electromagnetic and pulse operated.

7. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means. means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means including magnetic sheet holding means, said roll means being positioned to engage a trailing edge portion of a sheet engaged with said front stop means; and means for reversing rotation of said roll means whereby the latter retrieves the sheet from said work station; said means for moving a sheet sideways including a power operated pusher means along the other side of the feed path and engageable with a side edge of a sheet at said work station urging the other side edge of said sheet against said side stop means; said holding means being electromagnetic, said holding means and said pusher means being alternately energized. 

1. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning said stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means includes electromagnetic sheet holding means divided into first and second portions spaced along the rotational axis of said roller means and positioned on opposite sides of a center line for said feed path, and means for energizing each of said portions while the other is deenergized.
 2. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means being positioned to engage a trailing edge portion of a sheet engaged with said front stop means; and means for reversing rotation of said roll means whereby the latter retrieves the sheet from said work station; means at said feeding station defining a support for a sheet having its leading edge portion engaged by said roll means; a receiving means to the rear of said roll means operatively positioned to receive sheets retrieved from the work station by said roll means; and means active upon reverse rotation of said roll means to direct sheets from said roll means to said receiving means; said receiving means being positioned below the support; said means active upon reverse rotation of said roll means including said support and means for tilting said support by raising its front edge above its rear edge and above said feed path.
 3. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said means for moving a sheet sideways including spring means along the other side of the feed path and engageable with a side edge of a sheet at said work station urging the other side edge of said sheet against said side stop means, said roll means including pulse operated electromagnetic sheet holding means.
 4. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said means for moving a sheet sideways including a power operated pusher means along the other side of the feed path and engageable with a side edge of a sheet at said work station urging the other side edge of said sheet against said side stop means, said roll means including electromagnetic sheet holding means, said holding means and said pusher means being alternately energized.
 5. Feeding and positioning apparatus for moving sheets along a feed path to a worK station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means including magnetic sheet holding means, said roll means being positioned to engage a trailing edge portion of a sheet engaged with said front stop means; and means for reversing rotation of said roll means whereby the latter retrieves the sheet from said work station, means at said feeding station defining a support for a sheet having its leading edge portion engaged by said roll means; a receiving means to the rear of said roll means operatively positioned to receive sheets retrieved from the work station by said roll means; and means active upon reverse rotation of said roll means to direct sheets from said roll means to said receiving means; said receiving means being positioned below the support; said means active upon reverse rotation of said roll means including said support and means for tilting said support by raising its front edge above its rear edge and above said feed path.
 6. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means including magnetic sheet holding means, said roll means being positioned to engage a trailing edge portion of a sheet engaged with said front stop means; and means for reversing rotation of said roll means whereby the latter retrieves the sheet from said work station; said means for moving a sheet sideways including spring means along the other side of the feed path and engageable with a side edge of a sheet at said work station urging the other side edge of said sheet against said side stop means; said sheet holding means being electromagnetic and pulse operated.
 7. Feeding and positioning apparatus for moving sheets along a feed path to a work station of a power operated machine from a supply station located to the rear thereof; said apparatus including positioning front stop means at said work station and disposed transverse to said feed path, positioning side stop means at said work station at one side of said feed path, power operated roll means disposed to the rear of said work station positioned to engage a sheet at said supply station and upon forward rotation of said roll means drive this sheet forward until movement thereof is arrested by engagement of its leading edge with said front stop means, means for moving a sheet sideways to move a side edge of a sheet at said work station against said side stop means, said roll means including magnetic sheet holding means, said roll means being positioned to engage a trailing edge portion of a sheet engaged with said front stop means; and means for reversing rotation of said roll means whereby the latter retrieves the sheet from said work station; said means for moving a sheet sIdeways including a power operated pusher means along the other side of the feed path and engageable with a side edge of a sheet at said work station urging the other side edge of said sheet against said side stop means; said holding means being electromagnetic, said holding means and said pusher means being alternately energized. 